With regard to the laterally diffused metal oxide semiconductor field-effect transistors (LDMOSFET), one of these structures forms a shallow trench isolation (STI) structure between a drain and a source, which is referred to as a STI structure laterally diffused metal oxide semiconductor field-effect transistor. Since the device requires to have a high breakdown voltage (off-BV) in some applications, it is an urgent problem to increase the off-BV of the device without increasing the area of LDMOS.